1. Field of the Invention
The present invention relates to a knitting tool, for example a selector sinker or a needle for a knitting machine, which has a flat shank and a narrow elongate control spring projecting therefrom. The control spring is disposed in a projecting manner in the region of a narrow side of the shank with one end of the control spring rigidly anchored in a slot-like opening in the shank which is oriented toward this narrow side.
2. Description of the Prior Art
DE-OS 1,585,211 discloses a circular knitting machine which performs electronic needle selection. The needles are controlled by pushers in the form of electromagnetically controlled selector sinkers which are pivoted radially back and forth, according to the pattern of the product to be knit. The selector sinkers are pivoted between an effective position and an ineffective position to thus be brought into and out of engagement with a cam track. A respective control spring projects from a narrow side of each selector sinker. Each control spring is in the form of a spring rod having one end anchored to the shank of the selector sinker. At its free end, the control spring is supported at an abutment on the needle cylinder and functions to reset the selector sinker.
In order to anchor the control spring in the shank of the selector sinker, an end section of the control spring is bent approximately in the manner of a hairpin and one arm of it is pressed into a slot-like opening in the shank. The opening becomes wider toward its inward end and the end section is clamped in the opening.
Since the end section of the control spring is merely clamped into the slot-like opening of the shank of the selector sinker and thus is held under tension in a friction lock, a danger exists that during long periods of operation, high dynamic stresses may cause the end section of the control spring to work itself to some extent laterally out of the slot-like opening, with the result that additional friction occurs in the associated guide channel for the needle and the selector sinker. This is undesirable. Moreover, uncontrolled changes in dimensions occasionally may occur in the position of the control spring relative to the selector sinker. This also adversely influences the operation of the knitting machine.
The same applies in principle to the selector sinker illustrated in FIG. 10 of U.S. Pat. No. 3,643,472. This selector sinker has a control spring which is clamped at one end into an opening extending with parallel sides approximately at a right angle to the longitudinal axis of the sinker. The spring is secured against movement in its axial direction by an end piece that is bent at a right angle. The opening therefore must have an essentially L-shape, which is not easy to produce from a manufacturing point of view.
Finally, DE-OS 2,327,585 discloses a circular knitting machine which operates with needles whose shanks are provided, for magnetic needle selection, with respective control springs which are anchored at one end. The control springs are manufactured of steel wire and have a circular cross section or are slightly rolled flat, that is, have flattened portions, or are punched out of thin spring steel sheet metal. The end section of each spring is fitted into a slot defined by parallel flanks in a corresponding needle shank, with individual, spaced embossed locations provided on the side walls of the slot. The end section is wedged into the slot to fix it in place. Although this produces a form-locking connection between the end of the control spring and the needle shank, the spaced embossed locations on the side walls of the slot do not ensure precise lateral alignment of the control spring relative to the needle shank. The end section of the control spring is hardened and is therefore not deformed during the wedging. Therefore, in this arrangement also the end section of the control spring could, over the course of time, be caused by the high dynamic stresses thereon to be worked somewhat free of the wedging, thus making the entire control spring rotationally movable, within limits, at its anchorage point. Moreover, the danger exists that the transverse forces generated during the wedging might widen the slot, in which case the upright dimension of the shank could be changed in an uncontrollable manner.